If using OFDMA has increased data rate in LTE then why was OFDMA not used in 3G, Since this technology has been known for more than 50 years ?

The Answer :The concept of OFDM is not new and is currently being used on various systems such as Wi-Fi and WiMAX.

In addition, it was even considered for UMTS back in 1998. One of the main reasons why it was not chosen at the time was the handset’s limited processing power and poor battery capabilities.

LTE was able to choose OFDM based access due to the fact mobile handset processing capabilities and battery performance have both improved. In addition, there is continual
pressure to produce more spectrally efficient systems.